An anti-corruption investigation led to the arrest of a worker at HMP Berwyn.
The 25-year-old woman was arrested on suspicion of misconduct in public office yesterday and remains in custody.
The arrest comes as part of ongoing anti-corruption, Operation Earthly.
Police have also conducted co-ordinated searches of an address in North Wales and a vehicle linked to the arrest, while specialist search teams searched identified parts of the prison.
Supt Jason Devonport, of North Wales Police, said: “Behaviour like this undermines the safety and security of the prison and those who work and visit Berwyn.
”This operation shows the strong relationship between criminal justice partners to reduce the risk of corruption in prisons.”